This invention relates to television picture enhancement, and in particular to means for controlling the gray scale of television video signals.
Video pictures with present television systems tend to become washed-out when there are bright lights in the viewed area or when part of the viewed area is much more brightly lit than other parts, or in certain other adverse lighting conditions. It has been common practice to vary the gain control by mechanical or electrical means in order to compensate for such conditions. This approach, however, results in the aforementioned washed-out effect on the television picture. Compressing or removing the extreme parts of the signal by means of limiters is another state-of-the-art solution to the problem. Unfortunately this method destroys the details in the picture. There currently exists, therefore, the need for means that will compensate for the effects of bright and uneven lighting in the viewed area of television pictures without introducing wash-out effects and without sacrificing picture detail. The present invention is directed toward satisfying such a need.